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Release: April 15, 2002

UI researchers examine structure of dental fillings, other materials

If you've ever wanted to examine the structure of an opaque object -- for example, a dental filling or porcelain vase -- you may be interested in research conducted by University of Iowa engineering and dentistry professors at the Iowa Advanced Technology Laboratories (IATL) Building.

Julie L.P. Jessop, assistant professor of chemical and biochemical engineering in the University of Iowa College of Engineering, and Steve Armstrong, assistant professor of operative dentistry in the College of Dentistry, are investigating changes in the chemical makeup of dental restoration components, including fillings. They do this by cutting filled tooth samples into segments and scanning the length of the sample to identify regions of change in the tooth dentin, the filling composite, and the interface between the two. Their research, however, is as much concerned with testing the device used to examine the materials as it is with the materials themselves. In particular, their research involves an extremely powerful and versatile new instrument -- a HoloLab 5000R Modular Research Spectrometer -- recently put into use at the UI's Optical Science and Technology Center (OSTC).

Jessop, who has received a prestigious National Science Foundation (NSF) Faculty Early Career Development (CAREER) Award, conducts research into photopolymerization, a light-based process widely used in the film, coating and ink industries, that is finding new uses in the biomedical, communications, automotive and aerospace fields. She says that she plans to use the spectrometer's ability to see below the surface of thin films and coatings.

"This technique, known as confocal microscopy, allows nondestructive depth profiling of samples," she says. She explains that a laser creates a Raman scattered light effect in a sample volume. The scattered light is separated at the collection pinhole, with only the light from the plane of focus proceeding through to the detector. The technique can help determine the curing rate of a polymer or the structure of a hybrid polymer as a function of sample depth.

She adds that the device is modular, meaning that it can be upgraded for use in other novel research activities. For example, Mark Arnold, OSTC director and chemistry professor in the College of Liberal Arts and Sciences, plans to use the spectrometer to determine the concentrations of chemicals in the blood. His research, in part, involves the development of a non-invasive monitor for use in treating juvenile diabetes.

In addition, she is working with a UI chemistry researcher to use the Raman spectrometer to look at films he has fabricated in his laboratory and to determine the state of the carbon in them. A company interested in using the Raman microscope to identify imperfections in fiber optic photopolymer coatings also has contacted her.

Jessop's start-up laboratory funds, the OSTC, the College of Engineering and the Office of the Vice President for Research provided funding for the $140,000 spectrometer, manufactured by Kaiser Optical Systems, Inc., a subsidiary of Rockwell Collins Corporation.